This Midcareer Investigator Award application seeks support to provide Dr. Freedland with protected time for patient-oriented research (POR) and to act as research mentor for junior faculty and 1 research fellow per year. Dr. Freedland's POR focuses on retrospective cohort studies with a transitioning emphasis on prospective clinical trials aimed at developing new and less toxic treatments to minimize prostate cancer treatment side effects and slow prostate cancer progression. Herein, he proposes a new trial comparing a carbohydrate-restricted diet vs. control for men with PSA recurrence after prostate cancer therapy aiming to slow the rate of PSA rise (lengthen the PSA doubling time), as an indirect measure of slowed prostate cancer growth. Secondary outcomes include weight loss and important prostate cancer biomarkers. Successful completion of this award will advance our understanding of lifestyle and other low toxicity interventions for prostate cancer as well as help educate the next generation of POR investigators.